Support GITHUB_SHA for creating permalinks

Author: jb3

pydis_core/exts/source.py

@@ -4,6 +4,7 @@
 from importlib import metadata
 from pathlib import Path
 from typing import NamedTuple, TYPE_CHECKING
+import os
 
 from discord import Embed
 from discord.ext import commands
@@ -160,6 +161,8 @@ def _get_source_link(self, source_item: object, source_type: _SourceType) -> tup
 
         if source_type == _SourceType.core_command or source_type == _SourceType.core_cog:
             version = f"v{metadata.version('pydis_core')}"
+        elif sha := os.getenv("GITHUB_SHA"):
+            version = sha
         else:
             version = "main"